Add update interval for progress bar

[srafi1]

Adds an optional update_interval for progress bars that allows the user to skip unnecessary renders for frequently updated iterators.

• Fixes Avoid rendering on highly frequent updates in progressbar #676

Checklist:

• Add tests that demonstrate the correct behavior of the change. Tests should fail without the change.
• Add or update relevant docs, in the docs folder and in code.
• Add an entry in CHANGES.rst summarizing the change and linking to the issue.
• Add .. versionchanged:: entries in any relevant code docs.
• Run pre-commit hooks and fix any issues.
• Run pytest and tox, no tests failed.

[davidism]

This is a good PR, but it's making me realize we're just slowly reimplementing tqdm without the design and focus of that library. I'll merge this, but I think I'm going to close any other progress bar feature requests.